Starch is formed by polymerization of glucose molecules, and is the most common form of storage of carbohydrate in cells. Starch has a general formula of (C6H10O5)n. Hydrolysis of starch to a disaccharide stage results in maltose having the chemical formula of C12H22O11. Complete hydrolysis of starch results in monosaccharide (glucose), the chemical formula of which being C6H12O6. There are two types of starch, namely, amylose and amylopectin. Amylose is a non-branched helical structure. Meanwhile, glucose units in amylopectin are linked in a linear manner with α(1→4) glycosidic bonds, while branching takes place with α(1→6) glycosidic bonds occurring every 24 to 30 glucose units.
Oxidized starch is a type of modified starch obtained by reacting starch with an oxidizing agent in an acidic, alkaline or neutral medium so as to oxidize the starch. Oxidized starch lowers the gelatinization temperature, reduces the hot-paste viscosity and increases the thermal stability of starch. The product has a clean white color, transparent paste, good film formation and good resistance to freeze-thaw. As a low-viscosity high-concentration thickener, oxidized starch is widely used in the textile, paper, food and fine chemical industries.
Oxidized starch is one of the modified starches in early uses and researches. Oxidation with hypochlorous acid was already adopted in actual production as early as in the 18th century.
Hydroxyl groups in the starch molecule can be oxidized to carboxyl groups by oxides such as sodium hypochlorite, hydrogen peroxide and ozone.
There are already a wide range of applications of oxidized starch in the industries. Examples of common application of oxidized starch include the paper industry such as coatings or surface sizing, the adhesive industry, the textile industry and the food industry. Traditionally, oxidized starch is prepared by performing oxidation with alkali metal hypochlorite, which is a relatively inexpensive oxidizing agent. Since the oxidizing agent is usually alkali metal hypochlorite, the greater the amount of the oxidizing agent, the greater the risk that the oxidation products at the end of the reaction contain a certain level of chlorine. The reason is apparent in that the presence of chlorine is much undesired in terms of (public) health and the environment.
Cellulose, chitosan and starch are presently the three main classes of polysaccharide haemostatic material. The haemostatic principles of polysaccharide haemostatic materials differ from one type to another. For example, while the haemostatic principles of cellulose and starch both include three types of haemostatic effect, namely, physical, chemical and physiological, there is still difference in the process of physical haemostasis between cellulose and starch. Cellulose exerts physical haemostatic effect mainly by clogging the rupture of capillaries with the material. On the other hand, starch exerts physical haemostatic effect mainly by generating an internal suction due to the swelling of absorbent material, in which the internal suction allows the haemostatic material to adsorb to tangible components, thereby forming a mechanical blood clot. Meanwhile, the chemical and physiological haemostatic principles of cellulose and starch are the same.
Polysaccharide absorbable haemostatic materials are natural macromolecular materials present in a large quantity in nature. Due to various benefits such as a rich source, low prices, good biocompatibility, readily degraded and absorbed in the human body, and low incidence of adverse reactions, polysaccharide has become the focus of current researches in haemostatic material.